Off-the-Record (OTR) Messaging for Pidgin

Allows you to have private conversations over instant messaging when 
talking on Pidgin by providing:
- Encryption: No one else can read your instant messages.
- Authentication: You are assured the correspondent is who you think it is.
- Deniability: The messages you send do not have digital signatures that 
  are checkable by a third party.
- Perfect forward secrecy: If you lose control of your private keys,
  no previous conversation is compromised.

This requires libotr.
